Discovery of a Series of Pyrazinone RORγ Antagonists and Identification of the Clinical Candidate BI 730357.

The interleukin (IL)-23/T helper (Th)17 axis plays a critical role in autoimmune diseases, and there is an increasing number of biologic therapies that target IL-23 and IL-17. The transcription factor retinoic acid receptor-related orphan nuclear receptor γt (RORγt) is important for the activation and differentiation of Th17 cells and thus is an attractive pharmacologic target for the treatment of Th17-mediated diseases. A novel series of pyrazinone RORγ antagonists was discovered through hybridization of two distinct screening hits and scaffold hopping. The series offers attractive potency and selectivity in combination with favorable druglike properties, such as metabolic stability and aqueous solubility. Lead optimization identified a clinical candidate, compound (S)-11 (BI 730357), for the treatment of autoimmune diseases.

RORγt inhibition selectively targets IL-17 producing iNKT and γδ-T cells enriched in Spondyloarthritis patients.

Dysregulated IL-23/IL-17 responses have been linked to psoriatic arthritis and other forms of spondyloarthritides (SpA). RORγt, the key Thelper17 (Th17) cell transcriptional regulator, is also expressed by subsets of innate-like T cells, including invariant natural killer T (iNKT) and γδ-T cells, but their contribution to SpA is still unclear. Here we describe the presence of particular RORγt+T-betloPLZF- iNKT and γδ-hi T cell subsets in healthy peripheral blood. RORγt+ iNKT and γδ-hi T cells show IL-23 mediated Th17-like immune responses and were clearly enriched within inflamed joints of SpA patients where they act as major IL-17 secretors. SpA derived iNKT and γδ-T cells showed unique and Th17-skewed phenotype and gene expression profiles. Strikingly, RORγt inhibition blocked γδ17 and iNKT17 cell function while selectively sparing IL-22+ subsets. Overall, our findings highlight a unique diversity of human RORγt+ T cells and underscore the potential of RORγt antagonism to modulate aberrant type 17 responses.

Identification of pharmacological inhibitors of the MEK5/ERK5 pathway.

We have identified two novel MEK5 inhibitors, BIX02188 and BIX02189, which inhibited catalytic function of purified, MEK5 enzyme. The MEK5 inhibitors blocked phosphorylation of ERK5, without affecting phosphorylation of ERK1/2 in sorbitol-stimulated HeLa cells. The compounds also inhibited transcriptional activation of MEF2C, a downstream substrate of the MEK5/ERK5 signaling cascade, in a cellular trans-reporter assay system. These inhibitors offer novel pharmacological tools to better characterize the role of the MEK5/ERK5 pathway in various biological systems.